The receivers of prior art wireless communication systems have used radio frequency (RF) filters with wider pass bands than required to conform to the channel spacing of the transmissions. This has been done to accommodate a sufficiently large local oscillator (LO) tuning error in order to reduce the cost of the receivers, which have to be retuned to the center of the transmission channel during a tuning period. The use of the wider pass bands has resulted in a requirement for transmission-free "guard" bands surrounding each channel, thereby leaving some portions of the spectrum unused.
Modern wireless communication systems have developed new physical layers employing highly bandwidth-efficient modulation techniques, such as quadrature amplitude modulation (QAM), which can fit onto narrowband channels. Given the scarcity of radio spectrum, it would be highly desirable to utilize the unused portions of the spectrum of the prior art communication systems for transmitting at least a portion of one of the new narrowband channels.
Thus, what is needed is a method and apparatus in a wireless communication system for facilitating a sending of a first transmission over a first channel to a first receiver that requires a transmission-free guard band during the tuning period, and further for accommodating a second transmission on a second channel that overlaps with spectrum occupied by the guard band, the second transmission sent concurrently with the first transmission.